Fluoropolymers have been long known and have been used in a variety of applications because of several desirable properties such as heat resistance, chemical resistance, weatherability, UV-stability, low friction and anti-stick properties, etc.
Commonly known or commercially employed fluoropolymers include polytetrafluoroethene (PTFE), copolymers of tetrafluoroethene (TFE) and hexafluoropropene (HFP) (such copolymers are also referred to as FEP polymers), copolymers of tetrafluoroethene and perfluoroalkoxy copolymers (such copolymers are also referred to as PFA), copolymers of ethene and tetrafluoroethene (such copolymers are also referred to as ETFE polymers), copolymers of tetrafluoroethene, hexafluoropropene and vinylidene fluoride (VDF) (such copolymers also referred to as THV) and polyvinylidene fluoride polymers (PVDF) and others.
Fluoropolymers have been used to improve the thermal and chemical resistance of a substrate or to provide anti stick or low friction properties to a substrate, for example by coating or impregnating the substrate with the fluoropolymers. The fluoropolymers may be applied to the substrate by liquid coating techniques if they are provided as a liquid formulation, such, as for example, as aqueous dispersions.
Fluoropolymer dispersions can be conveniently produced by aqueous emulsion polymerization employing fluorinated monomers, one or more radical reaction initiators and a suitable emulsifier. Fluorinated alkanoic acids of the type CF3—(CF2)6—COO− with n being an integer of 6 to 8, and in particular perfluorooctanoic acid (n=6) and its salts, have been the emulsifier of choice in the aqueous emulsion polymerization of fluoromonomers for the last decades. Recently also other types of fluorinated emulsifiers for example fluorinated polyether acids have been employed. Fluorinated polyether acids may be generally more biodegradable than fluorinated alkanoic acids.
There is a continuous need to improve the properties and processing of fluoropolymer dispersions containing low amounts of the more biodegradable fluorinated polyether emulsifiers.